This invention relates to an artificial turf product designed to simulate the basic properties of natural turf and a method for making it.
Artificial turf athletic mats for use for golf practice, or on a golf driving range, desirably have a particular set of physical properties. First, it is desirable to utilize a grass-like surface to simulate a grass golf course natural turf and surface. Second, the underlying such a mat is very important because golfers swing long, relatively heavy clubs, with great force. Should the club head ground on an unyielding surface, the surface, the club, and the golfer, may be injured. Third, on practice ranges, the surfaces of golf mats are subject to great wear because of the high level of use and frequent abuse. Previously disclosed mats have been found to be less than entirely satisfactory because they do not effectively simulate natural conditions and they wear too rapidly when in use.
Golf tee shots require the golf club to be swung so that the head passes cleanly through the position of the ball without impacting the ground surface. Practice surfaces used at driving ranges for tee shots should, however, deform to allow passage of the club head should the golfer strike the ball inexpertly and the club head inadvertently make contact with the practice surface. The surface should remain substantially undamaged so that a golfer may put in the hours of practice needed to obtain the desired level of proficiency. Previously disclosed mats have not satisfactorily met this need.
Golf fairway shots require the golf club to be swung so that the head passes through the position of the ball and on into the ground surface so as to displace a portion of turf, a xe2x80x9cdivot.xe2x80x9d Practice surfaces for fairway shots should deform to allow passage of the club head, provide sufficient resistance to give the xe2x80x9cfeelxe2x80x9d of taking a divot, and remain undamaged so that a golfer may put in the hours of practice need to obtain the desired level of proficiency.
Natural turf has a structure that can be described as four general layers. Each layer has properties that affect the performance of the overall playing surface. The layers differ by function and the type of material they have in them. The layers are described herein as the grass layer, the vegetative layer, the root-biomass layer and the root-soil layer. The grass layer consists largely of the grass blades on which the ball lies when in play. The primary variable characteristic of this layer is the length of the grass blades. On a golf course fairway, grass is generally maintained at a uniform level that varies depending upon the species of grass used on the course. For example, xe2x80x9cBent grassxe2x80x9d courses are maintained at about 0.6 cm (xc2xc inch) and rye grass courses at about 1.25 cm (xc2xd inch). In the rough, the grass blade length may vary widely as discussed below.
The vegetative layer is the layer where the grass blades join into the main vegetative meristem (xe2x80x9cstemxe2x80x9d) of the grass plant and is the region from which the plant grows. The vegetative layer is thin, firm, springy and supportive. The support is formed by the connections between the grass blades of the first layer, the stems of the second layer and the roots of the third layer. The vegetative layer is generally 0.3 cm (xe2x85x9 inch) to 0.6 cm (xc2xc inch) high with stems about 2 mm ({fraction (3/32)} inch) in diameter depending on the grass species and the mown height of the grass. The overall height of the vegetative layer is directly proportional to the grass blade length, e.g., in 5 cm (2 inch) high rough the vegetative layer might be 1.25 cm (xc2xd inch) high and composed of stems 0.45 cm ({fraction (3/16)} inch) thick. Such rough offers substantial resistance to the passage of a club head. If grass grows past 1.9 cm (xc2xe inch) in height, it begins to form a thatch, a build-up of interwoven live and dead grass, which increases the depth and density of this layer to an extent unsuitable for golf. Thatch is one reason why rough is so difficult to play. Keeping the grass 1.25 cm (xc2xd inch) or less in height prevents the development of thatch and maintains direct access to the root-soil layer.
The structural integrity of the vegetative layer of the fairway offers little resistance to the passage of the club head because of the lack of thatch. The club head has sufficient mass and speed, and also has a sharp leading edge that enables it to cut through the turf. The integrity of the vegetative layer provides a vertical support matrix that holds a divot together and maintains the structure of the turf surrounding the divot until it is replaced. Without this structure a divot would fragment into its individual components. Dynamically, the divot flies just after and along the same relative path as the ball until air resistance slows it down.
The root-biomass layer of natural turf is extremely complex and is composed of the grass roots, living and dead organic material, mineral particles, air, water, and a variety of living organisms. The activities of the living organisms of the root-biomass layer (the biomass constantly work to break down minerals and other materials to particles of critical size. The action of living organisms has a significant effect on the health of soil and plant life, and also has important effects on the performance characteristics of the turf.
On a golf course the root-biomass layer is usually about 50-percent space and 50-percent solid material. Grass roots help living organisms break up the soil and allow air and water to penetrate into the ground. Roots also establish vertical and horizontal integrity. They grow down to access water and out to increase their surface area for absorbing nutrients. The natural growth of roots gives turf its ability to repair itself. The 50-percent of space is about half filled with water which forms a thin film over almost all particles and materials in the layer. Through the playing season decaying material builds up, and constant activity compacts the turf. Golf courses aerate the turf twice a year to remove a percentage of the solid material so as to alleviate compaction and maintain the 50/50 ratio. Below the first 5 cm (2 inches) the amount of space decreases with increasing depth.
The grass roots provide a structural integrity that holds the turf together in the face of natural forces and that holds a divot together when it is displaced by stroke of a golf club. In a divot struck from natural grass, the soil stays trapped in the roots of a divot so that turf rapidly regrows when the divot is replaced. However, the degree to which the other materials are present affects how a club head will cut through the soil. The root-biomass layer is usually 2-3 cm (an inch or so) thick, depending on the grass species and the soil type. The horizontal growth of roots forms a matrix throughout the biomass layer that keeps the soil consistently loose and elastic. Most horizontal root growth occurs in the top 3.8 cm (1xc2xd inches) and takes advantage of the nutrients present in the biomass layer. Roots penetrate significantly into the fourth layer. In summer, healthy grass roots grow 20-35 cm (8-14 inches) or more into the soil, depending on the species, the health of the soil, and the availability of water. Roots help link the third and fourth layers of the soil together and increase the flexibility of the root-soil layer. The third and fourth layers are also linked together by the physical interactions of the inorganic materials.
The fourth, or root-soil layer, consists of the soil below the horizontal roots of the root-biomass layer. Other than the roots, this layer is compositionally similar to the third layer. However, incidence of living organisms declines with depth and the density of the soil increases with depth due to increased packing of the soil. The root-soil layer provides a firm base that supports the flexibility of the top the layers. The root-soil layer extends indefinitely below the surface, but meaningful texture and air infiltration is found only in the upper 5 cm (2 inches) of the root-soil layer.
The grass on golf courses is deliberately cut to different lengths on different regions of the course. On fairways, the grass is usually cut to 1.25 cm (xc2xd inch) or less in height. This short grass makes playing conditions uniform and, permits more consistent play variability of the surface is diminished. The grass on greens and tees is usually cut to 0.6 cm (xc2xc inch) or less in height. The player has a great deal more control over the ball when the ball is so close to the ground. However, while the effect of the grass is diminished, the soil still has a significant role in affecting play.
The xe2x80x9croughxe2x80x9d of a golf course is of various lengths, generally no shorter than 2.5 cm (1 inch) and up to lengths of 7.5-10 cm (3-4 inches). A ball that is sitting down in deep rough, i.e. rough that is higher than 5 cm (2 inches), is very difficult to hit. Deep-rough grass is long and thick. It wraps around the club head and impedes its path to the ball. The ball will likely fly only a short distance compare distance the ball would fly if struck from the fairway. When the ball lies in short rough, several ball flights are possible, and the golfer ha little control over the distance in this situation as well. For example, if the grass acts as a tee, the ball sits up and a player could hit the ball much further than intended. Practice tee areas are cut to fairway height to make practice more consistent for the player.
In areas such as deep rough or a bunker, the golf club cannot cut through very well because there is just too much resistance. However, bunkers are made of sand, a type of soil preparation which is uniform and consistent in its reactive qualities. Skilled players can use their skill to hit accurate, consistent shots from bunkers.
Golf players deliver force to the surface in two ways. As the player makes a stroke, turf is impacted in two places. First, as the club head strikes down and through the turf surface and strikes the ball and natural turf, the force of the impact radiates out and down about 5-7.5 cm (2-3 inches). Second, the cleats on the shoes of the player create a shearing force on the turn, they push and twist through the stroke. The action of the golfer""s feet can cause substantial wear because at a practice area, the player stands and hits from one position.
In golf, force is delivered to the playing, or xe2x80x9cstriking,xe2x80x9d surface by the impact of the club head. Golf balls and golf clubs are designed to propel balls with backspin in order to affect and control the distance and direction of the flight of the ball. The club is designed to trap the ball between the face of the club and the ground so that the club face can exert a greater spin force on the ball. Forces are applied to a golf surface by the ball as it is trapped between the club head and the surface and by the club head directly. Forces are applied by the head as it swings through the line of travel, such forces may be delivered at speeds from about 100 cm/sec (a few miles per hour) up to 6700 cm per second (150 mile per hour) with compression loads from almost zero up to 140 Kg per square cm (2,000 pounds per square inch). Force is also delivered as the club head rotates about the axis of the club shaft. Shear forces may occur at up to 30xc2x0 from the direction of application of the direct force due to the rotation of the club shaft and the curvature of the club head path. The properties of the surface therefore have a great effect on results achieved with the club.
Natural turf practice areas are not readily available in urban areas, and many artificial turf devices have been developed over the years in an attempt to accurately simulate the feel of natural turf to the golfer. Previously disclosed artificial golf mats have portions that can move in response to the impact of a club head. Such malts use springs, rubber bands, or the like to provide a movable surface. Other golf mats have artificial turf surfaces made of belts that move along the path of travel of the club head. These devices have achieved some success, but in general have proved too complex, too unreliable, or too cumbersome or non-portable for regular golf use.
Other prior art discloses mats for golf that art a simple rubber mat, some embodiments having a pile surface and others having a textured rubber surface. Polyurethane has also been used to form a golf mat, usually by being adhered to the back of a tufted carpet material. Such arrangements have not been found acceptable because the polyurethane pad and the tufted layer easily de-laminate, and the entire mat often fails to withstand the blows from the club head and rips into pieces.
Still other disclosed golf practice mats comprise an artificial turf surface bonded to a base formed of foam rubber or other multilayered materials. These devices are less complex than those having movable portions, but again have not proven totally successful because they do not accurately simulate the feel of natural turf to the golfer and tend to de-laminate along their edges or internally as the layers of which they are composed become separated. Other mats that have been made sufficiently strongly to avoid delamination are rigid and provide an unnatural feel when used.
Golf mats conventionally used at driving ranges have a very short lifetime because of the damage done to the mat in the area of the tee. Golfers practicing their tee shots will often hit the mat with a club rather than cleanly hit the ball off of the tee. Previously disclosed mats cannot withstand the substantial forces received by the mat under these conditions and become locally worn beyond use.
Previously disclosed golf mats have tended to be vulnerable to weathering. Exposure to ultra-violet light, heat from the sun and water from rain affect the long term quality of any surface. The artificial materials previously disclosed have proved unable to resist the radiation and heating effects of the sun. Open-celled foams that have been previously disclosed have a tendency to absorb water when exposed to the elements. All foams suffer from hydrophilic degradation. Open-celled foams, however, absorb and hold moisture that promotes degradation.
Because the many previously disclosed golf mats are multilayer constructs, their novel aspects primarily involve the bond between an artificial grass surface and a supportive substrate.
The present invention relates generally to a turf-simulating device that provides a composite surface for golf or other use and that accurately simulates the four-layered structure of natural turf, e.g. to a golfer practicing golf shots thereon. A preferred embodiment of the present invention comprises a supportive base, tee-blocks and a playing surface formed from a turf-simulating composite mat. Together the three components simulate the four-layer structure and playing properties of natural turf.
The turf-simulating composite mat of the present invention forms a main pad and a pair of tee pads. The supportive base of the present invention has a rim that serves to locate the main pad and the tee-pads and to prevent lateral movement of the pads. The supportive base is formed of a centrally located primary core surrounded by a peripheral secondary core which has recesses in its upper surface to accept the tee-blocks of the invention. Tee-blocks with vertically oriented tee-holding flanges sit in the recesses in the secondary core and are held in place by the main pad and the tee pads which have appropriately shaped cut-outs which surround the vertically oriented tee-holding flanges. When assembled the top edges of the vertically oriented tee-holding flanges protrude slightly above the surface of the main pad and the tee pads to serve as buffers and resist the action of a golf club.
The turf-simulating composite mat comprises an integrally formed structure with a pile upper surface, a lateral-strength fabric and a supporting plastic-foam element which is fully described in U.S. Pat. No. 5,830,080 the disclosure of which is incorporated herein by reference. The supporting plastic-foam element is of substantially uniform density and can be made with different densities to match the playing conditions found in different geographic regions. The pile upper surface of the turf-simulating composite has a loop portion at its base. The loop portion interacts with the lateral-strength fabric and the supporting plastic-foam element to encapsulate and physically bond to the lateral-strength fabric and to the loop portion of the pile element. In a preferred embodiment of the invention the supporting plastic-foam element is 2.5 cm (1 inch) in depth.
The supportive base of the present invention provides a recess in which the turf-simulating composite mat lies. The supportive base comprises an engineered plastic primary core that simulates the root-soil layers of natural turf. In a preferred embodiment, the engineered plastic primary core is surrounded by a vacuum-formed secondary core with recesses therein to receive tee-blocks which are also an invention. The secondary core is bonded to the primary core by an inner elastomer ring and is also bonded to a surrounding elastomer rim which is shaped to form a recess that accepts the turf-simulating composite mat. The rimmed base provides a strong and consistent support for the mat and provides additional shock absorbing features to absorb and dissipate the impact shock from the club head. The materials of the base are strong and resilient enough to resist the continual movements when in use and to maintain a level and uniform striking surface.
The secondary core may also be made by a variety of processes including, thermo-forming, spin-forming, the so-called xe2x80x9cRIMxe2x80x9d process (Rotational Injection Molding), blow molding or the secondary core may be cast.
Certain embodiments of the base have integral reinforcing bars located within the secondary core. In other embodiments of the invention the secondary core is replaced by an integral foamed-plastic element that interacts with the primary core and a preformed elastomer rim. Embodiments of the secondary core generally have drain holes passing through to the soil to allow for the escape of water. Other embodiments of the secondary core have the form of a lattice having vertically oriented rectangular, hexagonal (e.g., honey-comb) or other shaped holes therethrough to allow for the escape of water.
The turf-simulating composite mat of the present invention is formed as a main pad and a tee pad that both fit within the base and which flank and surround a tee-receptive slit of a tee block to form a substantially flat surface from which a player can hit teed-up golf balls with a natural-like experience.
Tee-blocks of the present invention provide a tee-receptive slit lined with a tee-retaining self-tacky gel-foam material which allows natural-like positioning of tees. The tee-retaining self-tacky gel-foam material may be a cast or extruded thermoplastic material as listed in Table 4.
It is desirable that the look, feel, texture, and resilience of the artificial surface should closely simulate the properties of natural turf. Accordingly, it is an object of the present invention to provide an artificial surface for golf mats and driving ranges that has properties that simulate the properties of naturally grassed golf courses and is capable of withstanding heavy wear.
Particularly, the present invention effectively emulates the performance relationship of the natural layers between the grass and the underlying soil. Accordingly, the present invention provides acceptable levels of force feedback, and shock and vibration are rebounded at levels that provide a natural-like experience to the golfer. Emulation of the supporting properties of the root-biomass layer and the force-absorbing and force-reflecting properties of the root-soil layer are provided by the composite mat and the base of the present invention.
An object of the present invention is to provide a practice surface that simulates ground properties in a way that introduces a dynamic interaction at the same level that natural turf does. The invention disclosed herein effectively simulates the response of natural turf Natural turf responds to such forces as swing velocity, impact load, and energy absorption (as determined by deceleration of the club head) and provides a corresponding rebound. The effects of these forces are simulated by the present invention.
The durability of artificial depends on the compression set of the supportive structure and the resistance of the overall mat to degradation and abrasion. Compression set is determined by the cell memory of the material, i.e. the way individual cells are deformed and recover from deformation. Compression set and compression deflection are important properties of the materials used in the present invention. Compression set is also affected by the ability of a material to handle the long-term effects of passive and active loading.
Compression deflection is a measure of the ability of a material to handle immediate forces placed upon it, and also the consistency with which a material handles each individual event. Thus, a further object of the invention is to provide a surface that will deform and recover from deformation in a manner similar to natural turf. Urethane foams used in preferred embodiments of the present invention have superior consistency and provide these properties particularly well.
A method of making a turf-simulating composite is also part of the invention. A preferred embodiment of the device is made by first making a lateral-strength fabric with a pile surface formed thereon. The pile section is formed by passing a loop portion of each pile strand around the strands of the lateral-strength fabric so as to interactively associate the pile strands and the lateral-strength fabric and leave a filament portion upstanding from the fabric. A plastic-foam element is then formed so that the plastic foam encapsulates and physically bonds to the lateral-strength fabric and to the loop portion of the pile surface.
Another embodiment of the invention disclosed herein that simulates the four-layer properties of natural turf is a golf practice surface made of two independent components. In this embodiment the first component is a mat that comprises an integrally formed composite of pile, fabric and plastic foam, that simulates the grass, vegetative and root-biomass layers of natural soil. The second component of this embodiment is a rimmed base with a engineered plastic composite core that simulates the root-soil layers of natural turf. The second component provides a strong and consistent support for the mat and provides additional shock absorbing features to absorb and dissipate the impact shock from the club head. The base is made of material that is strong and resilient enough to resist the continual movements when in use and to maintain a level and uniform striking surface. The base mimics the relevant performance characteristics of the fourth layer of natural soil. Embodiments of the base may have drain holes passing through to the soil to allow for the escape of water. The present invention has no moving portions, has a simulated grass surface, has sufficient durability to be practicable and may be placed in the ground so that the surface is level with the natural turf. A particular advantage of the present invention is that rain water drains more rapidly from the playing surface than from natural turf thereby permitting a rapid resumption of play after irrigation or natural rain.
The pile of the composite mat has tufted strands that simulate grass and form a xe2x80x9chitting,xe2x80x9d or xe2x80x9cstriking,xe2x80x9d surface. The pile of the composite mat also has loop portions that interact with the lateral strands of the lateral-strength fabric. The plastic foam both encapsulates and physically and chemically bonds to both the lateral-strength fabric and to the looped portions of the pile section to form an integral structure that simulates how the vegetative layer and soil-biomass layer are bonded in natural soil.
A preferred embodiment of the present invention provides a golf practice tee that has a pile made of texturized nylon yam with pile length of about 1.25 cm (xc2xd inch). In other embodiments of the invention the pile of the turf-simulating composite is made of texturized or untexturized nylon, polypropylene or polyolefin alloy, with or without an extruded coating. The properties of fibers that may be used in different embodiments of the inventions are shown in Table 1. Properties of fibers shown are for illustrative purposes, those of skill in the art will realize that other fibers with other properties may be used within the spirit of the invention.
Other embodiments of the golf practice tee device of the present invention have a pile that is made of strands of texturized nylon yarn or a polyolefin alloy with extruded coating. The loop portions of the pile are tufted, woven, or knitted into a lateral-strength fabric made of polypropylene, aramid, or nylon. Other fibers that may be used to form the lateral strength fabric are listed in Table 1. Other fabric formed from fibers listed in Table 2 which provide a springy horizontal matrix may also be used.
Still another embodiment of the invention has a double-ply fabric in which the first ply is a polypropylene type cloth, and the second fabric ply is a spun bonded pick-weave polypropylene fabric. Fabrics suitable for use in the present invention have from 5 to 10 strands per cm (13 to 24 strands per inch). That is, the xe2x80x9cgridxe2x80x9d of the fabric will be from 5xc3x975 to 10xc3x9710 strands per cm (13xc3x9713 to 24xc3x9724 strands per square inch). Preferably it is envisaged that the fabric will be from 6xc3x976 to 8xc3x978 stands per square cm (15xc3x9715 to 21xc3x9721 strands per square inch). Most preferably fabrics with 7.2xc3x977.2 strands per square cm (18xc3x9718 strands per square inch) have been found to most suitable.
Other embodiments of the invention have a 0.15 cm ({fraction (1/16)} inch) to 0.6 cm (xc2xc inch) thick pile loop-portion that interacts with the lateral-strength fabric.
The foam elements of the invention are formed to have densities and resilient properties that differ depending on the particular use to which the embodiment is to be put. Generally, polyurethane foams may be used for the foam elements of the turf simulating composite of the invention. Polyurethane engineered elements of the present invention are integrally-skinned foams made by preparing a polymerization mixture by mixing an isocyanate source known conventionally in the trade as xe2x80x9cComponent Axe2x80x9d with a polyol source that contains a blowing agent and a catalyst, xe2x80x9cComponent B.xe2x80x9d An extensive description of processes for forming polyurethanes and compositions of Components A and B, is found in U.S. Pat. No. 5,451,612, the disclosure of which is incorporated herein by reference. Generally however, the blowing age Component B includes a carbonate source, water and an acid source that upon reaction with Component A generates a gas, carbon dioxide, that foams the polymerizing urethanes to form a engineered plastic. Polyurethane engineered elements of the present invention are made by mixing Component A and Component B placing the mixture in a mold to form an integrally-skinned polyurethane element as disclosed in U.S. Pat. No. 5,451,612.
Polyurethane engineered elements of the present invention are made of different denser and resiliencies by mixing Component A and Component B in different ratios. Ratios of Component A to Component B that are found to yield foams particularly suited to the purposes of the present invention range from 45:100, to 51:100. Other ratios are, however, envisaged to be used to make embodiments of the invention to simulate particular conditions. The properties of flexible, integrally-skinned, microcellular polyurethanes are shown in Table 3.
In preferred embodiments of the invention the plastic foam element of the turf-simulating composite is a high-performance foam material with an average cell size of about 0.08 mm and a thickness of about 2.5 cm (1 inch).
The base of a preferred embodiment of the invention is an integrally rimmed base with a primary core and a surrounding secondary core. The primary core is about 3.8 cm (1xc2xd inches) thick and can be thermo-formed polyethylene or polypropylene or engineered polypropylene with a fenestrated or honey-comb structure. Preferably the primary core is an engineered polypropylene. The secondary core of the present invention is about 3.8 cm (1xc2xd inches) thick and is preferably formed of polyethylene or polypropylene. In alternative embodiments of the invention the secondary core may be a foamed plastic element.
The secondary core is made with a recess approximately 1.9 cm (xc2xe inch) in depth pre-formed in what will be its upper surface. The recess receives and locates an inverted T-shaped tee-block. The recess, together with the thickness of the composite mat, provides a 5 cm (2 inch) standard tee 5 cm (2 inches) of adjustment for tee height. Accordingly, when the turf simulating surface of the present invention is assembled, the inverted T-shaped tee-block is fitted into the recess in the composite base and the main pad and the tee-pad then fit over tee-block so as to hold the tee-block in place.
Embodiments of the invention described herein additionally comprise an inner elastomer ring cast between the primary core and the secondary core and an elastomer rim cast around the elements of the primary and secondary cores of the base so that the rim becomes integrally associated with the core elements of the base. In preferred embodiments of the invention the edges of the core elements of the base are shaped so that the core elements, the inner elastomer ring and the rim physically interdigitate and chemically bond together when the base is formed.
The integrally formed rim of the base has a generally trapezoidal cross-section with a vertical internal surface that, together with the upper surface of the primary and secondary cores, forms a recess that the turf-simulating composite fits into. The trapezoidal rim provides an angled external surface that tapers outwards so that the natural soil around the device can be laid over the angled external surface to securely hold the device down when it is used. Generally the base may be angled from 30xc2x0 to 50xc2x0 from the vertical, preferably at 40xc2x0 from the vertical, however other angles suitable for use in the present invention will be known to those of skill in the art.
Embodiments of the present invention may include a reinforcing bar at the front and rear edges of the base. The reinforcing bars may be of any polygonal shape and are positioned in a pre-formed groove in the secondary core and integrally sealed therein. Preferably the reinforcing bar is aluminum or an alloy thereof and is 2.54 by 0.229 cm (1 inch by 0.090 inch) and is a 150 cm (5 feet) long strip. Reinforcing bars this size provide lateral stability against deflection and creep warping, and maintain horizontal fexibility but impact absorption and reduced bounce. Reinforcing bars may also be fiberglass, carbon fiber, steel, graphite, polyamides or rigid plastics.
An elastomeric plastic is cast into the base mold thereby bonding the primary core, the secondary core and the reinforcing bars together to form the rimmed base. As the elastomer is cast it flows to completely surround and encapsulate the reinforcing bars, core, and to form the rim. Also, as the elastomer cures, it expands to tightly interdigitate with the rough surface of the staggered vertical grooves of the core and so forms an integral structure.
Embodiments of the invention have replaceable tee-blocks that are set into the surface of the golf practice tee device so as to be substantially flush with the surface. Tee-blocks of the present invention have a seam which accepts standard tees. The tee-block comprises a bi-material element comprising a first material which is a dense foam which is cast or extruded to formed an inverted T-shaped element with a centrally positioned slit in the upwardly pointing xe2x80x9clegxe2x80x9d of the T-shape. The centrally-positioned slit is lined with a second material comprising a soft tee-retaining gel-foam elastomer. The gel-foam elastomer may be cast, in which case the casting process bonds the gel-foam elastomer to the dense foam inverted T-shaped element. Alternatively, the gel-foam elastomer may be separately produced and affixed in the T-shaped element, for example by the use of two-sided adhesive tape.
Definitions and Terms
Densityxe2x80x94The denseness of a material expressed as mass per unit volume, either as pounds-per-cubic-inch, or as grams per cubic centimeter.
Elongation at Break (xe2x80x9cExe2x80x9d)xe2x80x94Also called xe2x80x9cbreak elongationxe2x80x9d is the change in length of a specimen compared to its no-load length at the moment of failure under load. E is usually expressed as percent (%).
Filamentxe2x80x94The smallest component of a yam.
Modulus (xe2x80x9cMxe2x80x9d)xe2x80x94The property describing the resistance of a material to extension. Young""s modulus or the xe2x80x9cmodulus of elasticityxe2x80x9d represents the stress required to produce a given stretch or change in length. Modulus is area-specific, that is, it is expressed base on a unit of the original (i.e. no load) cross section. Modulus units are the same as those for xe2x80x9ctenacity.xe2x80x9d
Tenacity/tensile strength (xe2x80x9cTxe2x80x9d)xe2x80x94The ultimate strength exhibited by a material at the moment of failure based on a unit of the original (i.e. no-load) cross section. The most commonly used units are xe2x80x9cpounds-per-square-inchxe2x80x9d (psi); xe2x80x9cgrams per denierxe2x80x9d (gpd); xe2x80x9cNewtons-per-texxe2x80x9d (N/tex), and xe2x80x9cpascalsxe2x80x9d (Pa). Frequently, the term xe2x80x9ctensile strengthxe2x80x9d is used synonymously with xe2x80x9cultimate stress.xe2x80x9d
Yarnxe2x80x94Bundle or assembly of individual filaments.
Composite Matxe2x80x94A turf-simulating composite of the present invention with an artificial grass-like surface, a lateral strength fabric and a foamed-plastic core. xe2x80x9cMain-padsxe2x80x9d and xe2x80x9ctee-padsxe2x80x9d of the present invention are composite mats.
Rimmed Basexe2x80x94A pre-assembled base in which tee-pads, the main-pad and tee-pads fit to form the assembled turf-simulating surface of the present invention.
Engineeredxe2x80x94A form of construction of a plastic cellular panel or sheet referred to in the industry as xe2x80x9choney-comb constructionxe2x80x9d or xe2x80x9ccellular construction.xe2x80x9d Generally such cellular panels have a fenestrated core which is scrimmed top and bottom with a non-woven plastic fabric. The xe2x80x9cprimary corexe2x80x9d of the present invention is a cellular panel.
The present invention relates to an artificial turf that accurately simulates the basic structures, properties, and dynamics of the grass, vegetative and third layers of natural turf. Accordingly, although embodiments of the invention disclosed herein relate to a novel golf practice surface, application of the present invention to other sports uses is envisaged.